1. Field of the Invention
The present invention relates to a valve of an aerosol container for example, intended for dispensing a product at an essentially constant flow rate, for example, a cosmetic product. The invention is most particularly suited for dispensing deodorants or hairstyling products, especially lacquers or mousses.
2. Description of the Related Art
Modernly, the problem of variations in performance between the initial use of a container and the final use is encountered in the field of aerosol dispensers. These problems arise, in particular, in devices in which the product is pressurized by means of a compressed gas, especially carbon dioxide or nitrogen dioxide. In such devices, the gas is either directly in contact with the product or isolated from the product by a piston or a bag containing the product. The variations in flow rate and/or pressure are directly associated with the pressure drops inside the container, which inevitably cause a drop in product outlet flow rate.
It is known, as evidenced by EP-A-0,450,990, to provide a regulator inside a valve so as to regulate the outlet flow rate of the dispensed product. Such regulating systems entail, among other things, the use of a calibrated spring, controlling the extent to which an orifice is open or closed, depending on the pressure inside the regulating chamber relative to the set-point pressure imposed by the spring. In operation, a raised pressure in the regulating chamber causes the inlet orifice of the regulating chamber to close until, once a sufficient quantity of product contained in the regulating chamber has been discharged, the pressure in the chamber returns to the nominal pressure. One of the drawbacks associated with such a regulating system stems from the fact that the calibrated spring is arranged in a part of the valve body in communication with the product. The pressure in this part of the valve body is a partial pressure somewhere between atmospheric pressure and the pressure inside the container. Such a pressure depends on the internal pressure of the container and on any pressure drops incurred as far as the product outlet orifice. The pressure also depends on the product contained in the container, particularly on its vapour pressure. Thus, for each new formulation, it is necessary to use a different calibrated spring, which makes the system somewhat inflexible. Furthermore, the means of shutting off the outlet orifice are not secured to the piston, and this results in a less precise flow rate regulation.
FR-A-2,711,973 describes a push-button, in which a regulating system is arranged. The drawbacks of such a system are mainly of two fold. On one hand, the regulating system takes up a significant amount of space in the push-button, which leaves little latitude for designing the supply to the outlet nozzle or the diffusing system and spray mechanism. On the other hand, between uses, the means of shutting off the regulating chamber are in communication with the outside of the container, and therefore with the air, which entails a high risk of the shutter "sticking", especially in the case of products with a high resin content.